The compound (R)-5-carbamoyl-3-N,N-dicyclobutylamino-8-fluoro-3,4-dihydro-2H-1-benzopyran, which also may be named (R)-3-N,N-dicyclobutylamino-8-fluoro-3,4-dihydro-2H-1-benzopyran-5-carboxamide and pharmaceutically acceptable salts thereof are described in WO 95/11891.
The disclosed hydrochloride salt of (R)-3-N,N-dicyclobutylamino-8-fluoro-3,4-dihydro-2H-1-benzopyran-5-carboxamide is hygroscopic and thus physically unstable during manufacturing as well as during storage.